Oil and gas wells and other types of wells such as geothermal wells are typically drilled from the well surface to a desired downhole location using a rotary drilling rig, drill pipe, and drill bits. The drill hole or wellbore for conveying subsurface oil, gas, or other formation fluids are typically drilled in stages. For example, a wellbore may be first drilled with a column of drill pipe (a drill string) and a first drill bit having a particular diameter. At a desired depth for a first portion of the wellbore, the drill string and drill bit are removed from the wellbore. Tubular members of smaller diameter, often referred to as casing or a casing string, may then be placed in the first portion of the wellbore. An annulus formed between the inside diameter of the wellbore and the outside diameter of the casing string is generally filled with cement. The cement provides support for the casing, isolates downhole formations or subterranean strata from each other, and prevents contaminating fluids from entering the well.
Often, the next step in drilling the wellbore is to pass the drill string having a second smaller diameter drill bit through the first casing string and drill another portion of the wellbore to a selected depth beyond the depth of the first casing string, and a second casing string is installed. Many wells have two or more casing strings with different inside diameters installed in a telescoping manner from the well surface to a desired downhole location. For example, a first casing string may be installed from the well surface to a depth of 500 to 1,000 feet. The first casing string may have an outside diameter of nine and five/eighths inches (9 ⅝″). A second casing string may be installed extending from the surface to the desired depth or from proximate the downhole end of the first casing string to a desired depth of 9,000 or 10,000 feet. The second casing string may have an outside diameter of approximately seven inches (7″). This sequence of drilling wellbores and installing casing strings may be repeated as many times as necessary, with smaller and smaller components until the ultimate desired depth or downhole location of the wellbore has been achieved.
In recent years, “premium” (i.e., proprietary) connections have been designed specifically to overcome the challenges encountered with extended reach drilling operations, as well as the horizontal drilling needed for the recovery of shale gas by hydraulic fracturing (“fracking”) of gas-bearing shale formations. Premium connections can withstand higher drilling pressures and temperatures than standard American Petroleum Institute (API) connections of the prior art. Premium connections also have consistent make-up parameters due to the tight manufacturing tolerances, and possess higher tensile and compressive strengths and burst and collapse ratings than demonstrated by standard API connections of the prior art. Although premium connections are generally more leak resistant than standard API connections, the typical premium coupled connection nonetheless has two potential leak paths associated with the two separate ends of the coupled pins. The present invention solves the problem of two potential leak paths by machining two different integral seal geometries on separate pin ends of mated tubular members which come into contact on assembly to create a single, metal-to-metal, leak-tight, internal seal.